I agree with the link that mondo-broady has listed but another that you can try is this one:
Focus ST - UK
I was a member of this forum for a long time when I lived in the UK and had one of these bad boys. I only had my car for one year and never got round do doing any tuning mods.
One of the best mods for the 5 pot engine is the Mountune 260 upgrade
Mountune UK in terms of extra power for cost. Read this story about one of these cars embrassed the new RS
ST-v- RS
Have a good look on the ST website as it has a massive amount of knowledge and this is where all the guys on the XR5turbo forum get their information.